The present invention relates to the production of cast metal articles, and more specifically, to an apparatus and a method for holding a mold that is being filled and for transferring a mold filled with molten metal from a pouring station while moving an empty mold onto said pouring station.
In the manufacture of cast metal articles such as railway wheels, it is important from a cost savings and energy savings point of view to produce such wheels as rapidly as possible while maintaining the accuracy necessary to produce near finish castings. A typical wheel casting plant layout is shown in U.S. Pat. No. 2,999,281. A cope or top mold section is placed on top of a drag or bottom mold section to form a complete mold. Usually the mold is a reusable graphite mold. When the completed mold is moved along a conveyor to a pick up station adjacent the pouring station, a pick-up crane is used to lift the mold and place it on the pouring station above the pouring tank. The mold is located above the pouring tank because a bottom pressure pouring method is used to inject the molten metal into the mold. The ladle containing the molten metal is placed within a pouring tank. The pouring tank is capable of being pressurized with air, thereby forcing the molten metal upwardly through a refractory pouring tube into the bottom of the mold.
Prior to filling the mold, the mold must be held in place, usually by air cylinders which extend downwardly to contact the cope. Further, a mold stopper assembly must be lowered, again by air cylinder, over the stopper hole in the mold. Finally, a riser height control mechanism must be lowered into the mold riser whereby the height of the molten metal in the riser is determined and hence the pouring operation is automatically controlled. These three mechanisms, the hold down cylinders, the mold stopper and the riser height control mechanism, were previously located on the mold set down crane legs used to pick up the filled mold and transfer it to the mold set down location from where the mold would continue for processing along conveyors.
The mold set down crane and the mold pick up crane are each comprised of a column assembly having two legs, and both column assemblies are mounted on a single top frame assembly. Such top frame assembly is capable of lateral movements along secondary girders, which secondary girders themselves comprise a crane assembly mounted on main girders giving the secondary girders the capability of moving longitudinally with relation to the pouring station. Because of the mounting of the pick up crane and set down crane on a single top frame assembly, their lateral movements along the secondary girders are simultaneous and of equal lateral dimension.
In the pouring sequence of the previously known arrangement, a mold just filled with molten metal is at the pouring station and a second, empty mold is at the mold pick up location. The mold hold down assembly, mold stopper and riser height control are attached to the set down crane, and, after pouring is completed, are raised from the mold. The set down crane then raises the filled mold while the pick up crane raises an empty mold. The frame assembly supporting both cranes is moved laterally along the secondary girders. The filled mold is placed at the set down location by the set down crane and the empty mold is placed at the pouring station by the pick up crane. The set down crane and the pick up crane are then moved via their frame assembly laterally along the secondary girders. When the set down crane reaches the pouring station, the mold hold down assembly and riser height control are lowered to the empty mold and the pouring operation begins. The mold stopper is lowered after the mold has been filled.
It is an object of the present invention to provide an improved pouring station mold handling arrangement.